Add intersection with cylinders

src/Geometry/Vector.hs

@@ -2,6 +2,7 @@
 
 module Geometry.Vector where
 
+import Linear
 import Geometry.Data
 
 -- | Moves from two to three dimensions, adding zero in z direction.
@@ -218,3 +219,7 @@ xyzV4 (V4 x y z _) = V3 x y z
 xyV3 :: V3 a -> V2 a
 {-# INLINE xyV3 #-}
 xyV3 (V3 x y _) = V2 x y
+
+reflectInNormal :: (Metric v,Fractional a,Num (v a)) => v a -> v a -> v a
+{-# INLINE reflectInNormal #-}
+reflectInNormal n v = v - (2 * project n v)